It's 20 years since I've visited Auckland Botanic Gardens in Manurewa and, in that time, it has grown from a burgeoning great idea into a mature, magnificent 64ha park. The rolling terrain is beautifully landscaped and complemented by a number of linked lakes. Like all good botanic gardens, sections are devoted to specific plant species and themes. And, I'm told, more than 10,000 different plant species.

It is botanically impressive but the 38 sculptures, placed in a harmonious way with the arboreal landscape, make this a pleasurable and inspiring 2-3km walk.

The fourth biennial Sculpture in the Gardens is underway and 23 temporary pieces, by New Zealand's best sculptors, are included. The garden also has 15 sculptural pieces that are permanently part of the landscape.

This is not a fast walk. I stop to look at all the sculptures and occasionally befuddle my navigation so need to backtrack - a trail guide, available at the reception, is essential. But it's an inspiring walk and pieces vary from lyrical to humorous and horrifying.

Art is a matter of individual taste but here are my 10 fabulous favourites

1. The edge of the terrace of the entrance and visitor centre is graced with three giant bronze ants carrying pieces of leaves bigger than themselves. Atta Mediae by Samantha Lissette is both delicate and strong. One has to admire ants; they are selfless, work with passion and are always biting off things bigger than they can chew. Lissette, who often uses natural forms to question or comment on humanity, captures ants' beauty and dedication perfectly.

2. Christine Hellyar's Pineapple Twists, ironically placed in the nearby edibles area, comprises three large, finely crocheted tablemats that have been impregnated with pineapple-coloured resin, twisted in fanciful ways and perched on slender stalks. Though they're seriously solid, Hellyar captures the movement and delicacy of windblown crochet in a cheeky way. They seem to float, lighter than air, across the garden.

3. Michael Klaja and Gordon Smith's collaborative piece, Carving up the Land, is so powerful it's scary. This massive but absolutely realistic knife sticks into the earth as if it has just been thrust there. The main message is in the title, that we humans have attacked our land with violence and strength, greedily carving it up and devouring it. The subliminal messages, about physical violence, status and power, come from the knife. This beautiful brute will sell, to a bloke I bet, and it's a mere $29,000.

4.Oh Crabby, I Do Believe We're Rather Lost! by Jamie Pickernell is as sweet and humorous as the knife is not. A large bunny in a red-and-white striped swimsuit with his pet crab on a lead stands on the brow of the hill, scanning the horizon. He has human-like feet and hands and a rabbit face. His pet crab, with steel legs and a rock body, is a fine piece of craftsmanship. It reminds me of an eccentric, slightly confused gentleman taking his dog for a walk. Yes, we humans can be equally lost.

5. "Quardle oodle ardle wardle doodle," is the oft repeated chorus line of The Magpies, a poem by Denis Glover. In Over the Farm Gate, Bryan Verey has latched on to magpies, and this poem, and created a sculpture that captures the way of life of Kiwi farmers. The larger-than life magpie sits on a bigger-than-usual farm gate. The magpie's song is carved into the cross-beam that holds the gate together and scenes of early New Zealand farming are carved into the gate posts. It's fun, it's totally typical of my farming childhood and I like the referencing between poetry and art.

6. Across a large mown field, The White Horse by Ben Foster stands sedate and statuesque in an open space. It's ghostly and mysterious against the verdantly green background. I don't know what it means but it's irresistible and children run to it to pat its plastic flanks and stroke its nose.

7. I look for 7 Days by Jane Downes but omit to look up. When I do, I'm delighted with the seven finely patterned parasols floating on the breeze above me. These rusted-steel umbrellas are strung between two giant gum trees, their silhouettes gorgeously floral. This work is feminine and lyrical, art on air, and if I was allowed to choose just one of the 38 sculptures in the Botanical Garden this would be it.

8. Jeff Thomson does miraculous things with corrugated iron and, as the years go by, he increasingly works this hard, cutty material in an illusory manner. Home Sweet Home is a woven corrugated iron house. It looks as if it's woven from something soft, like old carpets or thick felt. But when I touch it I find it's hard and cold. Children love it. They run round it shrieking, jumping on the steps and hiding behind it.

9.Tree Man by James Wright looks best as a silhouette. The steel-made, giant human figure, with sturdy legs and arms out-stretched, morphs from the ground up into a tangled, leafy tree. Wright explores the relationship between man, nature growth and this piece, while referencing a similar idea, is as celebratory and joyful as Carving up the Land (3) is threatening and violent. In a nice moment of synchronicity, the sprayers are giving the Tree Man a good dousing.

10.Alterations by Louise Purvis is the winner of the McConnell Family Supreme Award of $10,000. It is reminiscent of a muscular glass house without the glass. It has an overlay of elegant and delicate building-type forms making it both fragile and strong. The straight, clear lines shriek "manmade" in contrast to the growing green curves in the surrounding gardens. Standing inside it, and looking out, frames and alters the way we see the natural world beyond. And that, it seems, is what good art is all about.